1. Field of the Invention
The various exemplary embodiments of the claimed invention relate to an arteriosclerosis diagnostic device, and in particular, a device for estimating the elasticity of arterial walls and determining the degree of arteriosclerosis.
2. Description of the Related Art
Modern medical care is dramatically progressing from day to day. However, most of the medical care is symptomatic treatment, and research of preventive medicine, which improves self-healing power on the basis of a daily lifestyle, has hardly advanced. An example of lifestyle-related diseases is arteriosclerosis. In the existing technologies, there are various methods, such as a direct method of evaluating a blood sugar level, cholesterol, and other components from a blood sample or a urine sample, and indirect method of estimating a disease in the body from a measured value of a blood pressure, pulsation, heartbeat, or respiratory sound. However, these techniques are insufficient in terms of monitoring of biometric information.
Japanese Unexamined Patent Application Publication No. 9-201361 proposes an arteriosclerosis diagnostic device that transmits and receives an ultrasonic beam to and from an object, obtains an echo signal, measures a time difference of arrival from a distance between two measurement locations, and calculates a pulse-wave propagation velocity. The device is intended to be used in diagnosis for arteriosclerosis by associating the above-mentioned calculated pulse-wave propagation velocity with the hardness of blood vessels.
However, the device described in Japanese Unexamined Patent Application Publication No. 9-201361 can obtain only the propagation velocity of a pulse wave propagating along an arterial wall (i.e., only displacement information), so there is a problem in that it is susceptible to external factors, such as an error resulting from a skin surface. Also, a calculated value is affected by the distance between two measurement locations. Hence, measurement widely varies among parts used in measurement. Furthermore, there exists a problem of the complexity and expensiveness of the measurement device.